How to test the air circuit of the solenoid valve

2022-07-26
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How to check the air circuit of the solenoid valve

how to deal with solenoid valve faults

the rated voltage of solenoid valve coil includes DC12V, DC24V, AC24V (50/60hz), AC110V (50/60hz), AC220V (50/60hz), AC380V (50/60hz). Generally, in electrical design, either AC220V (without switching power supply, low cost, simple circuit and easy maintenance) or DC24V (common safety voltage, switching power supply/solenoid valve coil are easy to repair and replace) shall be used

methods for detecting the quality of the solenoid valve: first supply the controlled medium (liquid and gas with pressure, the pressure value is the middle value of the pressure range used by the solenoid valve) to the solenoid valve, and then energize the solenoid valve coil. If the controlled medium changes from on to off or from off to on, the solenoid valve is good, otherwise it is a problem

common faults of solenoid valve

1. Coil short circuit or open circuit:

detection method: first measure its on-off with a multimeter, and the resistance value approaches zero or infinity, which indicates that the coil is short circuit or open circuit. If the measured resistance value is normal (about tens of ohms), it does not mean that the coil must be good (I once measured that the resistance value of a solenoid valve coil is about 50 ohms, but the solenoid valve cannot act. After replacing the coil, everything is normal). Please carry out the following final test: find a small screwdriver and put it near the metal rod threaded through the solenoid valve coil, and then energize the solenoid valve. If you feel magnetic, Then the solenoid valve coil is good, otherwise it is bad

treatment: replace the solenoid valve coil

2. Problem with plug/socket:

fault phenomenon:

if the solenoid valve has a plug/socket, there may be a problem with the metal reed of the socket (I have encountered it), a problem with the wiring on the plug (for example, the power line is connected to the grounding wire), and other reasons, the power supply cannot be sent to the coil. It is best to form a habit: screw the fixing screw after the plug is inserted into the socket, and screw the fixing nut after the valve core rod on the coil

if the plug of solenoid valve coil is equipped with LED power indicator, it should be connected correctly when DC power is used to drive the solenoid valve, otherwise the indicator will not be on. In addition, do not switch the power plugs with LED power indication at different voltage levels, which will cause the led to burn out/short circuit in the power supply (switch to the plug of low voltage level) or weak light emission of the LED (switch to the plug of high voltage level)

if there is no power indicator, the solenoid valve coil does not need to distinguish the polarity (unlike the transistor time relay with DC coil voltage and the intermediate relay with DC coil voltage connected in parallel with diode/resistance leakage circuit on the coil, it needs to distinguish the polarity)

treatment method: correct wiring errors, repair or replace plugs and sockets

3. Valve element problem:

fault phenomenon 1: when the pressure of the medium connected to the solenoid valve is normal, press the red manual button of the solenoid valve, and the solenoid valve does not respond (the pressure medium does not change), indicating that the valve element must be bad

treatment method: check whether there are problems in the medium, such as whether there is a lot of water in the compressed air (sometimes the oil-water separator does not play a great role, especially all seamless steel pipes need to be tested for mechanical properties. When the pipeline is poorly designed, there will be a lot of water in the compressed air to the solenoid valve), and whether there are many impurities in the liquid medium. Then clear the accumulated water or impurities in the solenoid valve and pipeline. If not, please repair (if you have time and patience and if necessary @_@) or replace the valve element, or simply replace the entire solenoid valve

fault symptom 2: after inspection, the coil is the original coil, and the magnetic property of the coil is normal when it is powered on, but the solenoid valve still does not act (at this time, the function of the manual button of the solenoid valve may be normal), indicating that the valve core is broken

treatment: please repair or replace the valve element, or simply replace the entire solenoid valve

as for the maintenance of the solenoid valve body, there are too many kinds of maintenance methods, so I can't say much about them. Here, I won't go into details about plastic film, wires and cables, waterproof coiled materials, metal wires, cartons and other materials

faults and troubleshooting of giant valves in emerging markets

I The solenoid valve does not work after being powered on

check whether the power wiring is poor → rewire and connect the connector

check whether the power voltage is within ± the working range - → the main purpose is to make the staff full of enthusiasm for the company to adjust whether the coil in the normal position range

is desoldered → reweld

the coil is short circuited → replace the coil

whether the working differential pressure is inappropriate → adjust the differential pressure → or replace the matching solenoid valve

the fluid temperature is too high → replace the matching solenoid valve

the main valve core and moving core of the solenoid valve are stuck due to impurities → clean it. If the seal is damaged, replace the seal and install the filter

the liquid viscosity is too high, the frequency is too high and the service life has reached → replace the product

II. The solenoid valve cannot be closed

the main valve core or the sealing element of the moving core is damaged → replace the sealing element

fluid temperature Whether the viscosity is too high → replace the matched solenoid valve

impurities enter the valve core or moving iron core of the solenoid valve → clean

the spring has reached its service life or deformed → replace

the orifice balance hole is blocked → clean in time

the working frequency is too high or the service life has reached → change the product or update the product

III. other conditions

internal leakage → check whether the seal is damaged, Whether the spring is poorly assembled

leaking → the connection is loose or the seal is damaged → tighten the screw or replace the seal

there is noise when energizing → the fastener on the head is loose and tightened. The voltage fluctuation is not within the allowable range. Adjust the voltage. Clean or replace the iron core timely in case of impurities or unevenness on the clamping surface

how to quickly judge whether the solenoid valve is good or bad on site

first, check whether the solenoid coil of the solenoid valve is faulty

give the opening or closing signal to the two position valve on DCS, and then check whether the solenoid valve is powered on or off. Generally, it is OK to listen to the sound on site

if you can't hear it, there must be a problem with the coil. Is there a problem with the solenoid valve itself? (explained below)

if there is a problem with the solenoid coil, first check the wiring to see if there is a virtual connection or a short circuit. If there is no problem on the circuit, the solenoid valve coil is burnt out. Remove the wiring of the solenoid valve and measure it with a multimeter. If there is an open circuit, the solenoid valve coil is burnt out. The reason is that the coil is damp, resulting in poor insulation and magnetic leakage, resulting in excessive current in the coil and burning. Therefore, it is necessary to prevent rainwater from entering the solenoid valve. In addition, the coil may be burnt out if the spring is too hard, the reaction force is too large, the coil turns are too few, and the suction is not enough

II. If the coil is good, it is the problem of the solenoid valve itself

generally, the valve can be opened from 1 to 0 at the manual adjustment position. If it can be opened, it indicates that it is indeed a coil problem. If it cannot be opened, it is OK to change the coil. If it cannot be opened, remove the solenoid valve to see if the valve core is stuck or blocked by foreign particles. CCl4 should be used for correct cleaning. However, considering that there are no conditions on site, gasoline can be used, and there is no water, After cleaning, the on-site instrument air can be used to blow dry. Remember the sequence of each component when disassembling. If you don't pay attention, it is easy to make mistakes when installing. If you remember the wrong sequence, even if you clean the solenoid valve, even if the solenoid valve has been connected, it still can't be opened

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